Htlc intercept greenlight

[vyomeshaudi6]

intercept for greenlight and lnd instance together. lnd need to be tested.

[roeierez]

@vyomeshaudi6 thanks for the PR and I am excited to get this going.
I think we need to organize the code a bit so it would be ready for handling two different LSPDs. For now let's assume they are not running simultaneously but if we design it right I think the move to running simultaneously would be easy as just different port of grpc to each of them, but this is later.
For now these are the structural changes that I see we need:

The original server.go contained all the LND logic, so I think we should not mix c-lightning logic with LND at this stage. One option is to

1. Rename the file to lnd_lspd.go with run method instead of main
2. Add clightning_lspd.go with run method that initialize the plugin and clightning stuff.
3. Then we can add a main.go that using a configuration flag to know which server to run.

The main file can handle also the generate keys if needed.
As the implementation gain progress we will see if some re-use is needed.

[roeierez]

Looks good! a small comment regarding env variable.

[roeierez]

Thanks @vyomeshaudi6 small comments and other than that Looks good to me.
We'll wait for @yaslama to review as well.

[JssDWt]

Closing this in favor of #22